It was a good year for polls. This time, they got the basic story of the election right: a Democratic House and a Republican Senate. And on average, the final polls were closer to the results than any election in a decade. Best of all, the polls were relatively unbiased, meaning that one party didn’t systematically overperform or underperform its final poll results.

But while the big picture is much better than in 2016, when the polls systematically underestimated Donald J. Trump in the battleground states, some details are eerily similar. The geographic distribution of polling error was much like in 2016, even though the average poll wasn’t particularly biased at all.

It was enough for election night to briefly feel reminiscent of 2016, as polls underestimated Republicans in several key states and races. It raises questions about whether polls remain vulnerable to a 2016-like error in 2020, when the race promises to be tighter and focused on the kinds of predominantly white, working-class states where the polls underestimated Republicans.